At Wits End--Engine Loss of Power, Backfires
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At Wits End--Engine Loss of Power, Backfires
I have a 95 Ram 5.2, automatic, 4x4. The truck is backfiring thru the intake, also has a lack of power. I've had the heads off and taken to machine shop twice, valves ground, new springs, new lifters, heads were purchased new. I've replaced all upper gaskets, all 3 sensors, checked fuel pressure(26psi), replaced cap and rotor with MSD copper, new 8.5mm MSD wires, new champ copper plugs. New Cat installed about 6 months ago, with new O2 sensor(only have 1).
I'm at wits end here. Any info would be a great help. Thanks
I'm at wits end here. Any info would be a great help. Thanks
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Joined: Jul 2010
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From: fargo, n.d
Fuel pressure should be up around 48psi. Cylinder is firing while intake valve is open. Have timing and fuel sync checked. Possible worn bushings on distributor shaft.? Triple check all wires are correct on the new cap for firing order. Welcome to DF. You will get some more responses in the morning.
Last edited by ReadRam; Dec 22, 2013 at 12:37 AM.
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Joined: Jun 2007
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From: Fond Du Lac, WI
Okay, let me see here...check your grounds, a loose ground would cause this issue. Check all your connectors...all the usual suspects. Certainly if immediately after installation it was fine and now it's not without acquiring significant miles and you've tackled the usual suspects (even with low fuel pressure it wont backfire, but it will throw codes for lean conditions once it exceeds 20%) My thoughts are on connectors, wires and grounds, be patient, check all of them. (That includes plug wires, I've crossed them before on accident) Fuel pressure btw needs to be checked with the engine off, key on within the first three seconds it should peak at base pressure, that number should be 37-41...anywhere in there is fine as that takes into account gauge innacuracy, temperature and so forth.
My point, I'll say it again. I think something came loose or rubbed the insulation off a wire. Visual inspection, put hands on everything, check the wire loom, is it rubbed through anywhere...are any of the wires especially brittle from exposure to oil or gas...
Ohh and the less likely but possible situation: Your engine has been running rich and it is now preigniting on the carbon deposits (dieseling)...In my case, if I checked everything and it came out ok, and the plugs looked ok, the engine would get inspected...Chinese timing chains...and everything else give me nightmares, if it jumped time...all these things are very small possibilities so go from easiest to that.
Ohh and all 5.2/5.9 engines, when the truck is 180 degrees or warmer, idling without the air conditioning on, the timing will be between 9 and 11 degrees stock. Hint hint you can check your timing with a light. The cam sensor and crank sensor are not correlation sensors on obd1 trucks. Timing on those is driven by the distro's cam sensor... I don't believe you can do the correlation test on that truck.
If it jumped time, the mark will be 8 or more degrees off from 10 degrees advanced at idle. It's an easy check if you have a timing light. Most engines will still run a tooth off... If the distro is worn out, that's another easy check, pull the cap, rock the rotor shaft in and out and side to side, try to turn it too...if it allows any of that by hand...it needs replacing.
That's enough to keep you busy for now.
My point, I'll say it again. I think something came loose or rubbed the insulation off a wire. Visual inspection, put hands on everything, check the wire loom, is it rubbed through anywhere...are any of the wires especially brittle from exposure to oil or gas...
Ohh and the less likely but possible situation: Your engine has been running rich and it is now preigniting on the carbon deposits (dieseling)...In my case, if I checked everything and it came out ok, and the plugs looked ok, the engine would get inspected...Chinese timing chains...and everything else give me nightmares, if it jumped time...all these things are very small possibilities so go from easiest to that.
Ohh and all 5.2/5.9 engines, when the truck is 180 degrees or warmer, idling without the air conditioning on, the timing will be between 9 and 11 degrees stock. Hint hint you can check your timing with a light. The cam sensor and crank sensor are not correlation sensors on obd1 trucks. Timing on those is driven by the distro's cam sensor... I don't believe you can do the correlation test on that truck.
If it jumped time, the mark will be 8 or more degrees off from 10 degrees advanced at idle. It's an easy check if you have a timing light. Most engines will still run a tooth off... If the distro is worn out, that's another easy check, pull the cap, rock the rotor shaft in and out and side to side, try to turn it too...if it allows any of that by hand...it needs replacing.
That's enough to keep you busy for now.
Last edited by army_greywolf; Dec 23, 2013 at 04:20 AM.
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Joined: Apr 2010
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From: Clayton MI
Crank sensor tells the PCM when to fire the coil.
Cam sensor tells the PCM which injector to fire, and when.
Cam sensor tells the PCM which injector to fire, and when.
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Joined: Jan 2011
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From: British Columbia, Canada
You've probably re-checked.
Fuel pressure 94-95-39lbs, changed to 49psi when OBD11 was introduced in '96. Please go back and re-visit your plenum gasket as your symptoms are very much an indicater of a bad gasket install. Your fuel sync (if you have a stock cam should be set to "0") if it is off can also cause pinging, backfires, and big loss of power. If you have more agressive cam go to "+4" on your fuel sync. Good luck with this as I have seen people chase this ghost before!
